Study On The Effects Of Composite Modification Of ZSM-5 Zeolite On Aromatics Selectivity In Methanol To Gasoline

Methanol to gasoline technology(MTG)can not only solve the problem of methanol overcapacity,but also reduce the dependence of China's energy demand on oil.Aiming at the problems of high aromatic in gasoline due to high strong acid content and MFI topological structure,which allow the existence of aromatic hydrocarbon cycle,in MTG process with HZSM-5 zeolite.In view of the HZSM-5 zeolite surface rich in adjustable acid properties and pore structure,considering HZSM-22(TON)and SAPO-11(AEL)zeolite not only has one-dimensional pore channel,but also weak surface acidity which lead to low aromatics content in gasoline in MTG process.The study started with the novel catalyst design,HZSM-5(MFI)was blended with HZSM-22(TON)or SAPO-11(AEL)respectively to prepare the composite zeolite and it's catalytic performance in MTG process was investigated.In this paper,the effects of processs conditions on the conversion of methanol,the yield of gasoline and the content of aromatics in gasoline were investigated with HZSM-5(80)zeolite as catalyst.The results showed that the optimized conditions for MTG were as follows: N2 flow rate 10mL·min-1,space velocity 2h-1,reaction temperature 380? and atmospheric pressure.On these conditions,the conversion of methanol,gasoline yield and selectivity of aromatics were 96.6%,38.96% and 49.36% respectively.HZSM-5/HZSM-22 composite zeolites with different acidity and pore structure were prepared by blending method.The physicochemical properties and catalytic performance of the composite zeolites were characterized means of XRD,FT-IR,BET and NH3-TPD characterization methods,and was studied on fixed bed microreactor respectively.The influence of Si/Al ratio,grain size,blending ratio,alkali modification and metal modification on the physicochemical properties and catalytic performance of HZSM-5/HZSM-22 composite zeolites were studied.The results indicated that the HZSM-5 zeolite with Si/Al ratio of 80 is suitable for the preparation of composite zeolite,blending with HZSM-22 zeolite by mass ratio 2:1.1%NiHZSM-5/HZSM-22 composite zeolite possessed a relatively large surface area of 209m2·g-1,medium strong acid content of 0.0095 mmol.g-1 and total acid content of 0.0704 mmol.g-1.The methanol conversion and gasoline yield are 98.61% and 45.34% respectively while the selectivity of aromatics was only approximately 37.19%.HZSM-5/SAPO-11 composite zeolites with different acidity and pore structure were prepared by blending method.The physicochemical properties and catalytic performance of the composite zeolites were characterized means of XRD,SEM,FT-IR,BET and NH3-TPD characterization methods,and was studied on fixed bed microreactor respectively.The influence of Si/Al ratio,grain size,blending ratio,and alkali modification on the physicochemical properties and catalytic performance of HZSM-5/SAPO-11 composite zeolites were studied.The results indicated that the HZSM-5 zeolite with Si/Al ratio of 38 is suitable for the preparation of composite zeolite,blending with SAPO-11 zeolite by mass ratio 2:1.(HZSM-5)0.1MNaOH/SAPO-11 composite zeolite possessed a relatively large surface area of 200m2·g-1,medium strong acid content of 0.0113 mmol.g-1 and total acid content of 0.0686 mmol.g-1.The methanol conversion and gasoline yield are 98.63% and 53.65% respectively while the selectivity of aromatics was 50.6%.The effects of different blending methods on the catalytic performance of the composite zeolites were investigated with(HZSM-5)0.1MNaOH and SAPO-11 zeolite as catalyst.The results indicated that evenly blending(HZSM-5)0.1MNaOH/SAPO-11 composite zeolite has the best catalytic performance.